Oxidized quinones signal onset of darkness directly to the cyanobacterial circadian oscillator
Oxidized quinones signal onset of darkness directly to the cyanobacterial circadian oscillator
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DOI：
10.1073/pnas.1216401109
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发表时间：
2012-10-30
影响因子：
11.1
通讯作者：
Golden, Susan S.
中科院分区：
文献类型：
--
作者：
Kim, Yong-Ick;Vinyard, David J.;Golden, Susan S.
蓝细菌的昼夜节律钟与昼夜周期的同步在没有明显的光感受器的情况下进行，留下了其具体机制的问题。昼夜节律振荡器可以在体外重建，其中两种蛋白质KaiA和KaiC的活性受到反映光合活性的代谢物的影响：KaiC磷酸化直接受到ATP/ADP比率的影响，KaiA对KaiC磷酸化的刺激被氧化的醌类阻断，但不被还原的醌类阻断。ATP/ADP比率的操纵可以重置重构的体外振荡器中KaiC磷酸化峰的定时。在这里，我们表明，脉冲氧化醌重置蓝藻生物钟在体外和体内。黑暗的开始导致体内质体醌库的突然氧化，这与ATP/ADP比率的逐渐降低相反，ATP/ADP比率在几个小时内福尔斯，直到光照开始。因此，这两种光合活性的代谢措施一致行动，以信号的开始和持续时间的黑暗蓝藻时钟。
Synchronization of the circadian clock in cyanobacteria with the day/night cycle proceeds without an obvious photoreceptor, leaving open the question of its specific mechanism. The circadian oscillator can be reconstituted in vitro, where the activities of two of its proteins, KaiA and KaiC, are affected by metabolites that reflect photosynthetic activity: KaiC phosphorylation is directly influenced by the ATP/ADP ratio, and KaiA stimulation of KaiC phosphorylation is blocked by oxidized, but not reduced, quinones. Manipulation of the ATP/ADP ratio can reset the timing of KaiC phosphorylation peaks in the reconstituted in vitro oscillator. Here, we show that pulses of oxidized quinones reset the cyanobacterial circadian clock both in vitro and in vivo. Onset of darkness causes an abrupt oxidation of the plastoquinone pool in vivo, which is in contrast to a gradual decrease in the ATP/ADP ratio that falls over the course of hours until the onset of light. Thus, these two metabolic measures of photosynthetic activity act in concert to signal both the onset and duration of darkness to the cyanobacterial clock.